[C++/66270] another may_alias crash

[Nathan Sidwell]

On 05/26/15 15:00, Nathan Sidwell wrote:
> On 05/25/15 21:18, Jason Merrill wrote:

>> Hmm, are you seeing a case where TYPE_CANONICAL (to_type) has the may_alias
>> attribute?
>
> Yes.  This occurs when the newly created TRCAA pointer is to a self-canonical
> type.  The
>   else if (TYPE_CANONICAL (to_type) != to_type)
> is false, so the newly created pointer is self-canonical too (and has TRCAA).
>
> If the canonical type should not have TRCAA we need to change the if condition to:
>    else if (TYPE_CANONICAL (to_type) != to_type || could_alias_all)
>
> where COULD_ALIAS_ALL is the incoming CAN_ALIAS_ALL value.  Does that make sense?
>
> Making that change does stop  the ICE I was seeing, but I've not done a full
> test yet.

Here's a patch implementing that change,  When build_pointer_type_for_mode is 
passed true for CAN_ALIAS_ALL, we force creating a canonical type, continuing to 
pass false for that pointer's creation.

booted & tested on x86-64-linux, ok?

nathan

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